Methods for establishing hydrophilic and hydrophobic areas on a surface of a substrate or film and associated microfluidic devices

ABSTRACT

Embodiments of the present disclosure are directed to methods, systems and devices, for precise and reduced spot-size capabilities using a laser to alter surfaces without chemical treatment, chemical waste, or chemical residues is provided for microfluidic systems (e.g., lab-on-a-disk, for example). In some embodiments, hydrophobic and super-hydrophilic areas can be created on surfaces in the same material at different areas and positions merely by using different laser settings (e.g., spot size, wavelength, spacing, and/or pulse duration). Accordingly, capillary forces that are a recurrent issue in a microfluidic devices (e.g., a centrifugal microfluidic disk) can be controlled for practical applications, including, for example when users handle the disks and insert a sample, the moment the substrate/device (e.g., disk) is placed in a system (e.g., a centrifugal system), capillary forces can take place and move the fluids, which becomes a problem for sequential bioassays taking place in substrate/device (e.g., disk). Thus, in some embodiments, the systems, devices and methods increase fluid control in microfluidic devices.

RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.17/832,543, filed Jun. 3, 2022 which is a continuation of InternationalPatent Application No. PCT/IB2021/060530, filed Nov. 13, 2021, whichclaims priority to and the benefit of U.S. Provisional PatentApplication No. 63/113,589, filed Nov. 13, 2020. Each of thesedisclosures is herein incorporated by reference it its entirety.

BACKGROUND

In all microfluidics, fluid control is essential for accuracy andprecision of sample-to-answer results. As microchannel dimensionsdecrease in microfluidic devices, forces inside of the channels becomemore dominant (e.g., increased capillary force depending on the surfacematerial and fluid used). A way of controlling the fluid inside of themicro-channels is by making passive valves inside these channels.

At the moment, the valves are restricted by completely changing theentire material or large surface areas to hydrophobic or hydrophilic,or, insertion of a material and elaborate chemical modification on largeareas of the microfluidic scale, specific areas of the micro-channels.

In the late 1990s, polymers supplanted silicon and glass as the materialof choice for the fabrication of micro total analysis systems (μTAS) andlab-on-a-chip devices. However, more recently, the microfluidics fieldhas explored more with thermoplastic polymers, which have enabledresearch facilities to rapidly prototype devices and transfer thetechnology to industrial applications. Thermoplastics are denselycrossed-linked, mouldable, are optically clear, durable, have low rawmaterial costs, as well as established manufacturing methods, makingthem attractive for mass production. One of the main thermoplastics usedfor microfabrication is poly (bisphenol A carbonate), otherwise known aspolycarbonate (PC). This optically transparent polymer has a highintrinsic absorption at 248 nm, in the deep-UV wavelength band, and lowabsorption in the near-infrared.

Some of its characteristics, such as low surface energy, high chemicalstability, poor surface absorbability and adhesion to other films andcoatings, make this polymer challenging to integrate into μTAS devices.Several studies have tried to tune PC's dielectric properties, surfacemodification (and wettability), effect of chemical doping in the PClaser ablation and micropatterning using excimer nanosecond laserirradiation. Femtosecond pulsed laser irradiation has also been used formicro hole drilling, micro pattern and lens arrays, on PC. Those studiesdemonstrated the formation of microstructures and how changing thewettability of polymer surfaces can be of great interest inmicrofluidics.

Wettability, characterized by hydrophilicity and hydrophobicity, plays arole in nanofluidic and microfluidic devices due to the high surfacearea-to-volume ratio, therefore, making the fluid more susceptible tothe surface tension on the microchannel walls.

The ability to tune the wettability of surfaces is a critical to precisefluid control in microfluidics, especially centrifugal microfluidicdiscs. Hydrophobic valves, have been used to control the burst speed(rotational speed at which the fluid opens the valve and move to anotherreservoir) or to stop capillary action and therefore allow better samplemetering and avoidance of cross contamination between chambers. In thecase of hydrophilic surfaces, the use of capillary force can be used todisplace fluid back to the centre of microfluidic disks allowing for theuse of timed valves and siphons.

SUMMARY

Embodiments of the present disclosure provides methods, systems anddevices for manipulating the burst frequency and pressure inmicrofluidics channels (e.g., of a microfluidic circuit) using lasersurface modification, to induce both super-hydrophilic (having a contactangle of zero or near zero) and hydrophobic (displaying a contact angleof 90 deg. or greater, and in some embodiments, of 150 deg. or greater(the latter corresponding to a super-hydrophobic area, with very lowcontact angle hysteresis)(<10° with water), areas on the same discmaterial, without any added reagents or post-treatment. Such embodimentsprovide crucial functionality for further miniaturization of devices inthe future.

Embodiments of the present disclosure enable the tuning of thewettability of surfaces—in some embodiments, both super-hydrophilic andhydrophobic, which is an important factor to precise fluid control inmicrofluidic (especially microfluidic disks). Hydrophobic valves, havebeen used to control the burst speed (rotational speed at which thefluid opens the valve and move to another reservoir) or to stopcapillary action and therefore allow better sample metering andavoidance of cross contamination between chambers. In the case ofsuper-hydrophilic surfaces, the use of capillary force can be used todisplace fluid back to the centre of microfluidic disks allowing for theuse of timed valves and siphons

Embodiments of the present disclosure introduce surface modificationtechniques using femto and nanosecond lasers which enable themodification of the wettability of a substrate, e.g., polycarbonate orother polymers, to respectively hydrophobic (and/or super-hydrophobicincluding contact angles of 150 degrees or higher), and/orsuper-hydrophilic, without chemical waste. In addition, techniquesaccording to some embodiments allow for site-specific modification,enabling more efficient fluid manipulation in microfluidic devices. Theapplicability of such physically altered surfaces as microfluidicvalves, according to some embodiments, were determined by consideringburst frequencies using centrifugal microfluidic systems (CMS or CMSs),which, in some embodiments, result in an increase in a pressure requiredto burst a hydrophobic valve, decrease for a hydrophilic valves.Hydrophilic valves according to some embodiments, can also function as ameans to increase a pressure necessary to burst the valves. Moreover, insome embodiments, the increase or decrease in pressure can be adjustedor tuned, according to some embodiments of the disclosure, according to,for example, channel dimensions and valve (hydrophobic or hydrophilic)patch area inside of the channel.

Accordingly, in some embodiments, a microfluidic surface/substrate(e.g., centrifuge disk) manufacturing method is provided and comprisesproviding a substrate having a surface (e.g., polycarbonate, forexample), which may be a disk, and at least one of:

-   -   establishing one or more hydrophobic areas (at high precision,        accuracy even at micro or nano areas) on the surface of a        substrate (e.g., microfluidic centrifuge disk or other        microfluidic device) by exposing such areas to a predetermined        wavelength or range of wavelengths of light (e.g., 800 nm, and        in some embodiments, e.g., infrared) via in some embodiments, a        femtosecond (for example) pulsed laser,    -   and in some embodiments, using a femtosecond pulsed laser,        where, the pulsed laser creates corresponding contact angles, in        some embodiments, 90 deg. or greater, 120 degrees or greater,        and, in some embodiments, greater than 150 deg.; and    -   establishing one or more super-hydrophilic areas on the surface        by exposing such areas to a UV nanosecond laser pulses, with        contact angles (in some embodiments), of zero or near zero        degrees.

In some embodiments, a microfluidic manufacturing method is provided andcomprises providing a polycarbonate (for example) disk (PD), andestablishing one or more fluid valves, and/or pathways on the surface ofthe PD comprising one or more combinations of hydrophobic andsuper-hydrophilic areas adjacent one another, where hydrophobic areasare established on the surface of PD by exposing such areas to apredetermined wavelength or wavelengths (e.g., 800 nm) via, for example,a femtosecond pulsed laser (FPL), where the FPL creates contact anglescorresponding to hydrophobicity (see, e.g., FIG. 2B), andsuper-hydrophilic areas are established on the surface of the PD byexposing such areas to a UV nanosecond laser pulses, and establishingcontact angles corresponding to super-hydrophilicity.

In some such embodiments, as noted above, one and/or another of thefollowing additional features, functionality, ranges of values, steps,and/or clarifications can be included (in some embodiments, a pluralityof, and in some embodiments, all of) yielding yet further embodiments:

-   -   contact angle related to the walls of the height of the channel        of between 37° and 45°;    -   contact angle related to the walls of the width of the channel        of between about 140° and 164°;    -   width of a microchannel of between about 650 and 750 μm;    -   height of a microchannel of between about 350 and 390 μm; and    -   pressure of between about 450 and 550 Pa.

The above-noted values, as well as other values disclosed hereinrelating to contact angles, pressures, andhydrophobicity/hydrophilicity, can be adjusted or tuned according tochannel dimensions and laser parameters.

In some embodiments, precise and reduced spot-size capabilities using alaser to alter surfaces, without chemical treatment, chemical waste, orchemical residues is provided for producing, for example,lab-on-a-disk-systems (as well as other microfluidic systems, e.g.,capillary sampling). In some embodiments, hydrophobic and/orsuper-hydrophilic can be created on surfaces in the same material (e.g.,polycarbonate, polymers) at different areas and positions merely byusing different laser settings (e.g., spot size, wavelength, spacing,and/or pulse, etc.). Accordingly, capillary forces, that are a recurrentissue in microfluidics, can be controlled for practical applications,including, for example when users handle a disk and insert the sample,the moment the disk is placed in a centrifugal system (for example),capillary forces can take place and move the fluids, which becomes aproblem for sequential bioassays taking place in disk. Thus, in someembodiments, the systems, devices and methods increase fluid control inthe microfluidic field in general (e.g., microfluidic disks, bloodsampling. Some embodiments can also be applied to open-microfluidiccircuits that may take advantage of having a hydrophobic orsuper-hydrophilic circuits or patches in specific circuit locations.

In some embodiments, such functionality can be achieved via at least oneof:

-   -   material modification using laser ablation;    -   formation of hydrophobic microfluidic valves;    -   formation of super-hydrophilic microfluidic valves;    -   formation of hydrophobic and/or super-hydrophilic surfaces in        the same material using different laser(s) parameters;    -   precise area, positioning and design of surface modification        (precise location and reduced size relative to any current        technology, enabling valves in micro-channels that can be used        for micro- and nano-fluidics), including, for example, formation        of hydrophobic and/or super-hydrophilic surfaces of/for/within        micro-channels;    -   and    -   use of alternate, or different spacings between lased and        non-lased areas (micro-areas) so as to tune a degree of        hydrophobicity and hydrophilicity of the material surface to a        desired amount.

In some embodiments, a microfluidic device manufacturing method isprovided and includes providing a substrate or film having a surface,and at least one of establishing one or more hydrophobic areas on thesurface of the substrate by exposing such areas to an IR wavelength of afirst pulsed laser, such that the first pulsed laser createspredetermined contact angles (e.g., static), and establishing one ormore super-hydrophilic areas on a different location on the same surfaceby exposing such areas to an UV wavelength from a second pulsed laser.

Such embodiments may include one and/or another of the followingadditional features, functionality, structure, steps, or clarifications(in some embodiments, a plurality of, in some embodiments, a majorityof, in some embodiments, substantially all of, and in some embodimentsall of), leading to yet further embodiments:

-   -   hydrophobic areas are created via machining using spot pulses        from a femtosecond laser;    -   and    -   the super-hydrophilic areas are created via machining using spot        pulses from a nanosecond laser.

In some embodiments, a microfluidic device manufacturing method ispresented and includes providing a one or more microfluidic channels ona surface of a substrate or film, and establishing one or more areasfluid valves, and/or pathways on the surface of the surface comprisingone or more combinations of hydrophobic and super-hydrophilic areas. Thehydrophobic areas are established on the surface of the substrate orfilm by exposing such areas to an IR wavelength of a first pulsed laser,where the first pulsed laser creates predetermined contact angles.Additionally, the super-hydrophilic areas are established on the surfaceof the surface or substrate by exposing such areas to a UV wavelength ofa second pulsed laser.

In some embodiments, a method of making a hydrophobic area and/or asuper-hydrophilic area on at least one surface of a polycarbonate (PC)substrate or film (for example), or on at least one surface of asubstrate or film material including properties similar to PC (forexample) is provided and includes machining, using laser ablation, atleast a portion of the at least one surface of the substrate or film viaa plurality of spot pulses from a laser to form, via a mask or a spatiallight modulator (SLM), at least one of a super-hydrophilic area and ahydrophobic area. For the super-hydrophilic area, the laser comprises ananosecond laser, and for the hydrophobic areas, the laser comprises afemtosecond laser.

Such embodiments may include one and/or an of the following additionalfeatures, functionality, structure, steps, or clarifications (in someembodiments, a plurality of, in some embodiments, a majority of, in someembodiments, substantially all of, and in some embodiments all of),leading to yet further embodiments:

-   -   the power of the nanosecond laser is configured based on the        depth of ablation desired;    -   a wavelength of the nanosecond laser is selected from the group        consisting of: between 150-400 nm, 150-350 nm, 150-300 nm,        150-250 nm, 150-200 nm, 200-400 nm, 250-400 nm, 300-400 nm        350-400 nm, and ranges therebetween;    -   a wavelength of the nanosecond laser is selected in the UV        range;    -   the nanosecond laser is a UV laser;    -   the femtosecond laser is an IR laser,    -   a wavelength of the femtosecond laser used as demonstration is        800 nm;    -   a wavelength of the nanosecond laser used as demonstration is        248 nm;    -   spot pulses of the nanosecond laser are delivered for a duration        selected from the group consisting of: between 0.1-50 ns,        between 0.1-40 ns, between 0.1-30 ns, between 0.1-20 ns, between        0.1-10 ns, between 0.1-5 ns, between 0.1-1 ns, between 0.5-50        ns, between 1-50 ns, between 5-50 ns, between 10-50 ns, between        15-50 ns, between 20-50 ns, between 25-50 ns, between 30-50 ns,        between 35-50 ns, between 40-50 ns, between 45-50 ns, and ranges        therebetween;    -   a repetition rate of the nanosecond laser is selected from the        group consisting of: between: 1 Hz-5 kHz, 1 Hz-4 kHz, 1 Hz-3        kHz, 1 Hz-2 kHz, 250 Hz-5 kHz, 250 Hz-4 kHz, 250 Hz-3 kHz, 500        Hz-5 kHz, 500 Hz-4 kHz, 500 Hz-5 kHz, 1-5 kHz, 1-4 kHz, 1-3 kHz,        1-2 kHz, 2-5 kHz, 2-4 kHz, 2-3 kHz, 3-5 kHz, 3-4 kHz, 4-5 kHz,        and ranges therebetween;    -   a spot pulse size established by the nanosecond laser is        selected from the group consisting of: between 10-10,000 μm²,        between 100-10,000 μm², between 250-10,000 μm², between        500-10,000 μm², between 750-10,000 μm², between 1,000-10,000        μm², between 2,000-10,000 μm², between 3,000-10,000 μm², between        4,000-10,000 μm², between 5,000-10,000 μm², between 6,000-10,000        μm², between 7,000-10,000 μm², between 8,000-10,000 μm², between        9,000-10,000 μm², between 10-1,000 μm², between 10-2,000 μm²,        between 10-3,000 μm², between 10-4,000 μm², between 10-5,000        μm², between 10-6,000 μm², between 10-7,000 μm², between        10-8,000 μm², between 10-9,000 μm², between 1,000-2,000 μm²,        between 1,000-3,000 μm², between 1,000-4,000 μm², between        1.000-5,000 μm², between 1,000-6,000 μm², between 1,000-7,000        μm², between 1.000-8,000 μm², between 1.000-9,000 μm², between        1,000-10,000 μm²; and ranges therebetween;    -   a spacing between spot pulses of the nanosecond laser is        selected from the group consisting of: between 1-100,000 nm,        between 1-75,000 nm, between 1-50,000 nm, between 1-25,000 nm,        between 1-20,000 nm, between 1-15,000 nm, between 1-10,000 nm,        between 1-5,000 nm, between 1-4,000 nm, between 1-3,000 nm,        between 1-2,000 nm, between 1-1,000 nm, between 1000-100,000 nm,        between 10,000-100,000 nm, between 25,000-100,000 nm, between        50,000-100,000 nm, between 75,000-100,000 nm, and ranges        therebetween;    -   a spacing between lines of spot pulses of the nanosecond laser        is selected from the group consisting of: between 1 nm-1000 μm,        between 1 nm-750 μm, between 1 nm-500 μm, between 1 nm-250 μm,        between 1 nm-100 μm, between 1 nm-50 μm, between 1 nm-10 μm,        between 1 nm-1 μm, between 10 nm-1000 μm, between 100 nm-1000        μm, between 1 μm-1000 μm, between 10 μm-1000 μm, between 100        μm-1000 μm, between 250 μm-1000 μm, between 500 μm-1000 μm,        between 750 μm-1000 μm, between 800 μm-1000 μm, between 900        μm-1000 μm, and ranges therebetween;    -   the nanosecond laser establishes the super-hydrophilic area        within a channel, and a static water contact angle is        established in the channel of the super-hydrophilic area of        greater than 99 deg. from a water droplet arranged between a top        and a bottom wall of a channel including the super-hydrophilic        are, or a completely wettable surface is formed where the water        contact angle is zero or near zero deg.;    -   the power of the femtosecond laser is configured based on the        depth of ablation desired;    -   the power of the femtosecond laser is selected from the group        consisting of: between 1-1000 mW, between 10-1000 mW, between        25-1000 mW, between 50-1000 mW, between 100-1000 mW, between        250-1000 mW, between 300-1000 mW, between 400-1000 mW, between        500-1000 mW, between 750-1000 mW, between 800-1000 mW, between        900-1000 mW, between 1-900 mW, between 1-800 mW, between 1-700        mW, between 1-600 mW, between 1-500 mW, between 1-400 mW,        between 1-300 mW, between 1-200 mW, between 1-100 mW, between        1-50 mW, between 1-25 mW, between 1-20 mW, between 1-15 mW,        between 1-10 mW, between 1-5 mW, and ranges therebetween;    -   a wavelength of the femtosecond laser is selected from the group        consisting of: between 680-1130 nm, between 680-1000 nm, between        680-900 nm, between 680-800 nm, between 680-700 nm, between        700-1130 nm, between 800-1130 nm, between 900-1130 nm, between        1000-1130 nm, and ranges therebetween;    -   spot pulses of the femtosecond laser are delivered for a        duration selected from the group consisting of: between 10-400        fs, between 25-400 fs, between 50-400 fs, between 75-400 fs,        between 100-400 fs, between 150-400 fs, between 200-400 fs,        between 250-400 fs, between 300-400 fs, between 350-400 fs,        between 10-300 fs, between 10-200 fs, between 10-100 fs, between        10-75 fs, between 10-50 fs, between 10-25 fs, and ranges        therebetween;    -   a repetition rate of the femtosecond laser is selected from the        group consisting of: between 500 Hz-300 kHz, between 500 Hz-200        kHz, between 500 Hz-100 kHz, between 500 Hz-50 kHz, between 500        Hz-10 kHz, between 500 Hz-5 kHz, between 500 Hz-1 kHz, between        500 Hz-750 Hz, between 750 Hz-300 kHz, between 1 kHz-300 kHz,        between 1.5 kHz-300 kHz, between 2 kHz-300 kHz, between 5        kHz-300 kHz, between 10 kHz-300 kHz, between 25 kHz-300 kHz,        between 50 kHz-300 kHz, between 100 kHz-300 kHz, between 150        kHz-300 kHz, between 200 kHz-300 kHz, between 250 kHz-300 kHz,        and ranges therebetween;    -   a spot size established by the femtosecond laser is selected        from the group consisting of: between 1-2500 μm², between 1-2000        μm², between 1-1500 μm², between 1-1000 μm², between 1-750 μm²,        between 1-500 μm², between 1-250 μm², between 1-100 μm², between        1-75 μm², between 1-50 μm², between 1-25 μm², between 1-10 μm²,        between 1-5 μm², between 1-2 μm², between 10-2500 μm², between        25-2500 μm², between 50-2500 μm², between 75-2500 μm², between        100-2500 μm², between 250-2500 μm², between 500-2500 μm²,        between 750-2500 μm², between 1000-2500 μm², between 1250-2500        μm², between 1500-2500 μm², between 1750-2500 μm², between        2000-2500 μm², between 2250-2500 μm², and ranges therebetween;    -   a spacing between spot pulses of the femtosecond laser is        selected from the group consisting of: between 500 nm-100 μm,        between 1 μm-100 μm, between 10 μm-100 μm, between 25 μm-100 μm,        between 50 μm-100 μm, between 75 μm-100 μm, between 80 μm-100        μm, between 90 μm-100 μm, between 500 nm-90 μm, between 500        nm-75 μm, between 500 nm-50 μm, between 500 nm-25 μm, between        500 nm-10 μm, between 500 nm-5 μm, between 500 nm-2 μm, between        500 nm-1 μm, and ranges therebetween;    -   a spacing between lines of spot pulses of the femtosecond laser        is selected from the group consisting of: between 100 nm-100 μm,        between 2500 nm-100 μm, between 500 nm-100 μm, between 750        nm-100 μm, between 1 μm-100 μm, between 2 μm-100 μm, between 5        μm-100 μm, between 10 μm-100 μm, between 25 μm-100 μm, between        30 μm-100 μm, between 40 μm-100 μm, between 50 μm-100 μm,        between 75 μm-100 μm, between 80 μm-100 μm, between 90 μm-100        μm, between 100 nm-100 μm, between 100 nm-75 μm, between 100        nm-50 μm, between 100 nm-25 μm, between 100 nm-20 μm, between        100 nm-10 μm, between 100 nm-5 μm, between 100 nm-2 μm, between        100 nm-1 μm, between 100 nm-900 nm, between 100 nm-750 nm,        between 100 nm-500 nm, between 100 nm-250 nm, between 100 nm-200        nm, between 100 nm-150 nm, and ranges therebetween;    -   the femtosecond laser establishes the hydrophobic areas within a        channel (as well as can establish the hydrophobic areas), such        that, a static contact angle of 90 deg. or greater, and in some        embodiments, 120 deg. or greater, and in some embodiments, 150        deg. or greater (super-hydrophobic areas);    -   the PC substrate or film is adhered to one or more additional        layers;    -   and    -   the one or more additional layers comprise one or more of: at        least one layer of polyethylene terephthalate (PET), an        additional layer of polycarbonate (PC) and including at least        one surface, at least one layer of polymethyl methacrylate        (PMMA) arranged adjacent at least one of the layers of PC, and        at least one layer of a pressure sensitive adhesive (PSA)        arranged between adjacent layers;

In some embodiments, a method for producing a material and/or surface ofa substrate or film is provided which includes at least one of one ormore super-hydrophilic and one or more hydrophobic areas, produced via ananosecond laser (for super-hydrophilic) and a femtosecond laser (forhydrophobic), respectively.

In some embodiments (which can include those listed above and elsewherein this disclosure), at least one of the super-hydrophilic areas and/orthe hydrophobic areas are configured as valves for a microfluidiccircuit, device, or channel.

In some embodiments, a system is provided for conducting any of themethods disclosed herein.

In some embodiments, a microfluidic device is provided and includes atleast one polymer (e.g., polycarbonate (PC) substrate or film, or amaterial including properties similar to PC), the substrate or filmincluding a predetermined thickness, and including at least one surface.At least a portion of the at least one surface of the at least onesubstrate of film is machined using laser ablation via a plurality ofspot pulses from a laser to form, with a mask or a spatial lightmodulators (SLM), at least one of a super-hydrophilic area and ahydrophobic area, via one or more passes. Each super-hydrophilic areaincludes a static contact angle of zero or near zero, and eachhydrophobic area includes a static contact angle of greater than 90deg., in some embodiments, greater than 120.0 deg., and in someembodiments, 150 deg. or greater (which can be consideredsuper-hydrophobic).

Further to such device embodiments, the polymer substrate or film (e.g.,PC) is adhered to one or more additional layers, and the one or moreadditional layers comprise one or more of: at least one layer ofpolyethylene terephthalate (PET), at least one layer of polycarbonate(PC), at least one layer of polymethyl methacrylate (PMMA) (which insome embodiments is arranged adjacent at least one of the layers of PCif used), and at least one layer of a pressure sensitive adhesive (PSA)arranged between adjacent layers.

In addition, in such device embodiments, the substrate or film comprisesor is part of a centrifugal microfluidic disk.

The methodology for some of the embodiments of the disclosure canestablish a combination of any of hydrophobic and super-hydrophilicareas (as well as hydrophilic if desired) on a substrate (e.g., apolymer, such as polycarbonate), with corresponding contact angles toattain of the forgoing can be established. Accordingly, in someembodiments, a nanosecond pulsed laser can used to effect a hydrophilicarea having a contract angle range of 30 degrees or less, or asuper-hydrophilic area having a contact angle range of approximatelyzero degrees, and a femtosecond laser can be used to effect ahydrophobic area having a contact angle range of 90 degrees or greater,in some embodiments, between 90 and 150 degrees, in some embodimentsbetween 120 and 150 deg., or a super-hydrophobic area having a contactangle of 150 degrees or higher.

Accordingly, in some embodiments, the hydrophilic areas produced via ananosecond laser, which can be tuned via associated parameters in viewof the amount of hydrophilicity desired, to product contact angles of(according to various embodiments), selected from the group consistingof: zero (0) or near zero (super-hydrophilic); between 0-1 deg.; between0-2 deg.; between 0-3 deg.; between 0-4 deg.; between 0-5 deg; between0-10 deg.; between 1-2 deg., between 1-3 deg., between 1-4 deg. between1-5 deg., between 1-10 deg., between 2-3 deg., between 2-4 deg., between2-5 deg., between 2-10 deg., between 3-4 deg., between 3-5 deg., between3-10 deg., between 4-5 deg., between 5-10 deg., between 0-50 deg.,between 0-40 deg., between 0-30 deg., between 0-20 deg., between 0-15deg., between 5-15 deg., between 5-20 deg., between 5-30 deg., between5-40 deg., between 5-50 degrees, between 10-20 deg., between 10-25 deg.,between 10-30 deg., between 10-40 deg., between 10-50 deg., between15-20 deg., between 15-25 deg., between 15-30 deg., between 15-40 deg.,between 15-50 deg., between 20-30 deg., between 20-40 deg., between20-50 deg., between 25-30 deg., between 25-40 deg., between 25-50 deg.,between 30-40 deg., between 30-50 deg., between 40-50 degrees, and rangetherebetween.

Accordingly, in some embodiments, the hydrophobic areas produced via afemtosecond laser, which can be tuned via associated parameters in viewof the amount of hydrophobicity desired, to product contact angles of(according to various embodiments), selected from the group consistingof: 90 deg. or greater, 95 deg. or greater, 100 deg. or greater, 110deg. or greater, 115 deg. or greater, 120 deg. or greater, 125 deg. orgreater, 130 deg. or greater, 135 deg. or greater, 140 deg. or greater,150 deg. or greater, between 90-100 deg., between 90-120 deg., between90-149 deg., between 100-120 deg., between 100-149 deg., between 110-120deg., between 110-149 deg., and between 120-149 deg., and rangestherebetween.

Additionally, in some embodiments, methods (and corresponding systemsand devices) to attain hydrophobicity and super-hydrophilicity, and finetuning thereof—and as noted in this disclosure—is via laser parameters,can produce surfaces/areas/portions corresponding tosuper-hydrophilicity or hydrophobicity.

These and other embodiments, features, functions, objects, andadvantages of the subject disclosure will become even clearer with thefollowing detailed description and accompanying drawings, a briefdescription of which follows immediately below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a plurality of different types of polymer beingassembled together to form a microfluidic disk, according to someembodiments;

FIG. 1B illustrates exemplary dimensions for various layers/substratesfor a microfluidic disk, according to some embodiments;

FIG. 1C illustrates an alignment tool, and various layers/substrates ofa microfluidic disk, for assembling the microfluidic disk, according tosome embodiments;

FIGS. 1D-1 and 1D-2 illustrate layers/substrates forming a microfluidicdisk, according to some embodiments;

FIG. 1E-1 through 1E-3 illustrate dimensions for at least some of thelayers and microfluidic elements or circuits, according to someembodiments;

FIG. 1F illustrates contact angles for microfluidics;

FIG. 2A-2B illustrates hydrophobic surfaces showing increase compared tothe control in Advancing (Adv), Receding (Rec) and Static (Sta) contactangles, with respect to spacing and power used, according to someembodiments;

FIG. 3 illustrates an image of surface roughness created on a polymer(e.g., PC) via a femtosecond laser to establish hydrophobicity,according to some embodiments;

FIG. 4 illustrates optical profile measurements on top view andcross-section views for hydrophobic surfaces at different line spacingfor a 13 mW laser, according to some embodiments;

FIG. 5 illustrates a super-hydrophilic surface created on asubstrate/film (e.g., PC), which shows crests and smooth surfacesproduced by a nanosecond laser, according to some embodiments;

FIG. 6 illustrate optical profile measurements on top view andcross-section view for super-hydrophilic surfaces at different linespacing, where waves (or microchannels formed by ablation within theablated area) and the melted area (white box) are also shown, accordingto some embodiments;

FIG. 7 illustrates, (top/left) a polymer (e.g., PC) unmodified surface(78.5 deg.), (top/right) a femtosecond laser modified surface (145deg.), and (bottom) a nanosecond laser modified surface and itssuper-hydrophilic wetting behaviour, according to some embodiments;

FIG. 8 illustrates, (left to right) an increase of hydrophobicity of thegold coated (blocked) super-hydrophilic surfaces created in a substrate(e.g., PC) according to 8, 10 and 12 μm line spacings, according to someembodiments;

FIG. 9 illustrates the ATR-FTIR spectra of the three polymer (e.g., PC)surfaces, normalized to the same height for the CH 2996 cm-1 andoverlaid for comparison, according to some embodiments;

FIG. 10 illustrates (left) top view of the channel showing θh(right-top) control, (right-centre) (super)hydrophobic and(right-bottom) super-hydrophilic surfaces and their wettability insideof a microchannel, according to some embodiments;

FIG. 11 illustrates three steps in a super-hydrophilic valve, accordingto some embodiments; and

FIG. 12 illustrates a theoretical P calculated using channel parameterssuch as contact angles and dimensions, according to some embodiments.

DETAILED DESCRIPTION

In some embodiments, a particular material having a surface (e.g.,polycarbonate) can be machined via laser ablation with different laserparameters to obtain super-hydrophilic, and hydrophobic areas (“modifiedarea” or “modified areas”). In addition, such materials can be part of alayered composite for, among many reasons, structural integrity.According, while some embodiments are discussed below correspond tolayered structures, where one and/or another of the layers include asurface machined via laser ablation to produce the modified areas (aswell as microfluidic circuits, microfluidic channels, and microfluidicvalves—the latter which can correspond to the modified areas), someembodiments of the disclosure are directed to surface modification of amaterial to effect modified areas, whether or not they are combined intoa layered composite.

One of skill in the art will appreciate that methods, systems anddevices, according to some embodiments, can produce (or be) microfluidicdevices/systems with merely hydrophobic and hydrophilic areas/surfaces(e.g., in addition to or in place of effecting hydrophobic andsuper-hydrophilic areas/surfaces

Various lasers and laser configurations/parameters are disclosed herein,a brief description of each is set out below.

As shown in FIG. 1A, in some embodiments, one or more, and in someembodiments, a plurality (e.g., two) of polymethyl methacrylate (PMMA)layers, which, in an embodiment, can include two different PMMA layers—a2.5 mm black layer (e.g.) and a 2.0 mm transparent layer (e.g.), coupledto a medical grade 125 μm pressure sensitive adhesive (PSA) (ARcare90106, Adhesive Research). In some embodiments, the two differentcolours serve to compare an effect of different backgrounds during, forexample, fat separation experiments. FIG. 1B illustrates exemplary, andnon-limiting, dimensions of disks and microfluidic circuits according tosome embodiments.

A bottom and a top part of microfluidic disks, according to someembodiments, can be cut using a continuous wave CO₂ laser (UniversalLaser Systems, VLS3.50, 30 W, 10.6 μm). The PMMA can be cut using 2.0lenses from Universal systems with working distance of 50.8 mm and 127μm spot size. The settings used to cut the 2.0 mm and 2.5 mm PMMA wererespectively 30 W at 11.25 mm/s and 30 W at 8.75 mm/s. In someembodiments, the PSA can also be cut using the same laser system, butdifferent lenses. A HPDFO (High Power Density Focusing Optics) lens wasused to generate a 25.4 μm spot size, and parameters used to cut the PSAcan be 1.35 W and 55 mm/s using the smaller spot size.

In some embodiments, modified surfaces can be made with 100 μmpolycarbonate (PC) films (e.g., Makrofol®), or materials having similarproperties. Hydrophilic PC surfaces can be fabricated using nanosecondUV laser machining (i.e., ablation), the specifications, according tosome embodiments, can be 248 nm, 5 ns pulse duration, 500 Hz repetitionrate, and can be a nanosecond laser from Xantos XS, Coherent Inc., USA)via a micromachining stage (e.g., IX-100C, JPSA Inc., USA). Creation ofa flat-top beam profile can be achieved with a physical mask, and/or aspatial light modulator (SLM)(SLM can be used so that many spots can bemachined/ablated at the same time). In some embodiments, an optimizedsetting can be approximately 100 μm² spot sizes (10 μm×10 μm), 1 μmspacing between shots, and 8, 10 and 12 μm spacing between lines. Insome embodiments, the power used for the nanosecond laser can be 0.5 mW.

In some embodiments, hydrophobic substrate surfaces (e.g., polymer—e.g.,polycarbonate) can be fabricated with femtosecond laser machining, thespecifications, according to some embodiments, can be 800 nm, 100 fspulse duration, 1 kHz, and can be a femtosecond laser from Legend Elite,Coherent Inc., USA (the micromachining stage (e.g., IX-100C, JPSA Inc.,USA.). In some embodiments, optimized femtosecond laser settings can be,2500 μm² square spot sizes (10 μm×10 μm), 1 μm spacing between shots,and 40, 45, 50, 55 μm spacing between lines (laser power can be 5 and 13mW, according to some embodiments).

In some embodiments, a total area machined using both the nanosecond andfemtosecond laser, can be approximately 6×6 mm, but in otherembodiments, can be lesser or greater. The super-hydrophilic andhydrophobic surfaces can be used as valves along channels inmicrofluidic circuits (e.g., provided on a centrifugal microfluidicdisk).

As noted above, in some embodiments, hydrophobic and mostsuper-hydrophilic valves created by the laser machining can be used tocreate hydrophobic and super-hydrophilic valves in centrifugalmicrofluidic disk channels. Accordingly, in some embodiments, suchcentrifugal microfluidic disks can include a plurality of layersincluding, a layer of 100 μm thick PC film (e.g., Makrofol®), a layer of125 μm thick pressure sensitive adhesive (PSA), e.g., AR-MH-90106, a 150μm thick layer of polyethylene film, and a 2 mm thick layer of PMMA(e.g., PSP Plastics).

Microfluidic circuits can be formed on a surface of a layer formed bytwo pressure sensitive adhesive (PSA) layers sandwiching a polyethyleneterephthalate (PET) sheet. These 3 layers can be attached and cut as asingle piece. The nanosecond laser can be used to cut the circuit layer(e.g., for super-hydrophilic areas).

Various layers can be cut using a nanosecond laser system with a 110 μmdiameter spot size, 0.8 μm spacing, 380 mW and two passes (e.g., aplurality of passes). A location of a start and an end of valves/surfacemodifications relative to the centre, can be, in some embodiments, 30.00mm and 31.27 mm, respectfully. In other embodiments, the laser settingscan be 100 μm diameter circle spot size, 0.8 μm spacing between shotsand 335 mW and 3 passes (e.g., a plurality of passes). Beam shapes ofthe laser can be formed via an iris to avoid losing laser power.

Another polymer layer(s) (e.g., PMMA) can be attached to a sheet of PSAand can be cut/configured using to form the base and top of the disk,which also contained the air release outputs and sample input ports. Insome embodiments, the PMMA layer can be cut via a continuous wave CO₂laser (e.g., Universal Laser Systems, VLS3.50, 30 W, 10.6 μm), which, insome embodiments includes a power of 30 W and a scan speed ofapproximately 12.5 mm/s (one and/or another of the power and speed canbe changes and/or scaled).

Microfluidic circuits machined on disks, according to some embodiments,can include one or more chambers configured for sample processing andanalysis. Disks can also be was optimised with modifications in designmade here include the angle of the chamber walls, dimensions, theaddition of a waste chamber for accurate measurement of an initialsample and manufacturing materials. A total volume of the sample chambercan be 12.3 μl, whereas a sample analysed after separation between ameasurement and waste chamber can be 5.1 μl.

In some embodiments, disks can include a plurality of layers, and insome embodiments, three (3) layers, which can be assembled together andaligned using three-point alignment as shown in FIG. 1C. The top layerof the disk, which in some embodiments, contains the sample or controlinlets and the pressure release valves. The central layer contains oneor more microfluidic circuits. The bottom layer can be used to, with thetop layer, sandwich the microfluidic circuit layer. In this alignmentmethod, the layers include alignment holes 102C and a rotor hole 104C.The cut layers are thus aligned using a three (3) poles that are of apredetermined diameter (e.g., 6 mm) and fitted to the alignment holes indisk. The disks were then pressed together using a roller.

FIG. 1D-1 illustrates the layers and assembly of a disk according tosome embodiments, and includes PMMA layer 102D-1 (grey, 102), PSA layer104D-1 (yellow, 104), PC layer 106D-1 (blue, 106), where the valves arearranged, and PET layer 108D-1 (brown/orange 108). The disk layerscross-section and its assembling. Exemplary dimensions are set out inFIG. 1E-1 , top layer of PMMA, FIG. 1E-2 , a PC layer showing thedistance of valves, and FIG. 1E-3 , fluidic circuit layer(s) beingmachined onto a PSA-PET-PSA assembly.

FIG. 1F is an illustration of a contact angle (θ) between a fluid andsolid (e.g., wall). Specifically, in the left-hand view, capillaryforces due to a hydrophilic surface push the liquid in the channel bywetting the walls and creating a concave meniscus. In the right-handview, a hydrophobic surface stops the liquid from moving through achannel creating a convex meniscus. As one of ordinary skill in the artwill appreciate (and is familiar with), a goniometer can be used tomeasure contact angles, and is essentially a platform to hold a sampleperpendicular to a camera, where the user can acquire a perpendicularpicture of a droplet relative to the surface being analysed.Measurements of contact angles correspond to how microchannels work interms of capillary force. In addition, surface energy can be measured toquantify the differences between different surfaces used to fabricatemicrofluidic devices (e.g., disks) and their effect on fluidmanipulation.

The contact angle can be correlated to surface tensions or energies viaYoung's equation (1).

γ_(sv)=γ_(sl)+γ_(lv) cos θ

Where, θ is the contact angle and γ_(sv), γ_(sl) and γ_(lv) arerespectively, the surface energy of solid-vapor, solid-liquid andliquid-vapor interfaces. There are several different methods to analysethe surface free energy (SFE) of solids. Some examples are Zisman,Fowkes, Wu, Equation-of-State (EOS) and Owens-Wendt-Rabel-Kaelble (OWRK)models.¹⁷⁰⁻¹⁷⁴ For example. The Wu method distinguishes the polar(γ_(sv) ^(p) and γ_(lv) ^(p)) and disperse components (γ_(sv) ^(d) andγ_(lv) ^(d)) of the surface energy. It is based on the reciprocal meanand force additivity, where the SFE of a solid can be calculated in theexpression (2).¹⁷²

$\gamma_{sl} = {\gamma_{sv} + \gamma_{lv} - {4\lbrack {\frac{\gamma_{sv}^{d}\gamma_{lv}^{d}}{( {\gamma_{sv}^{d} + \gamma_{lv}^{d}} )} - \frac{\gamma_{sv}^{p}\gamma_{lv}^{p}}{( {\gamma_{sv}^{p} + \gamma_{lv}^{p}} )}} \rbrack}}$

By combining Young's equation with the expression immediately above, theWu equation can be written to be associated with the contact angle asset out below (3).

${\frac{1}{4}{\gamma_{lv}( {1 + {\cos\theta}} )}} = \lbrack {\frac{\gamma_{sv}^{d}\gamma_{lv}^{d}}{( {\gamma_{sv}^{d} + \gamma_{lv}^{d}} )} - \frac{\gamma_{sv}^{p}\gamma_{lv}^{p}}{( {\gamma_{sv}^{p} + \gamma_{lv}^{p}} )}} \rbrack$

In this equation, there are two unknowns γ_(sv) ^(d) and γ_(sv) ^(p),and can be solved as a system of equations by using two differentliquids, therefore, using two different contact angles. Likewise, theOWRK method also distinguishes between the polar and the dispersivecomponents and it needs at least two liquids to solve for the solid SFE.However, it uses a harmonic mean to account for all the interactions inthe system, resulting in the equation below (4).

γ_(sl)=γ_(sv)+γ_(lv)−2√{square root over (γ_(lv) ^(d)γ_(sv)^(d))}−2√{square root over (γ_(lv) ^(p)γ_(sv) ^(p))}

Combining (1), with (3), results in equation (5) below:

${\frac{1}{2}{\gamma_{sl}( {1 + {\cos\theta}} )}} = {\sqrt{\gamma_{lv}^{d}\gamma_{sv}^{d}} + \sqrt{\gamma_{lv}^{p}\gamma_{sv}^{p}}}$

This equation can be rearranged to a linear form (y=mx+c) in order tofind the dispersive and polar components of the solid (γ_(sv) ^(d) andγ_(sv) ^(p)) as seen in the following equation (6):

$\frac{\gamma_{ls}( {1 + {\cos\theta}} )}{2\sqrt{\gamma_{lv}^{d}}} = {{\sqrt{\gamma_{sv}^{p}}\frac{\sqrt{\gamma_{lv}^{p}}}{\sqrt{\gamma_{lv}^{d}}}} + \sqrt{\gamma_{sv}^{d}}}$

The linear regression of two liquids results in a slope and intersectionthat can be used to calculate the polar component of the liquid and theintersection can be used to calculate the dispersive component.

Accordingly, in some embodiments use of a femtosecond laser allows forthe creation of a hydrophobic surface for static contact angles of, insome embodiments, greater than >136.0°±2.0 (hydrophobic surfaces canalso be created). In some embodiments, hydrophobicity is also dependenton the spacing between laser lines. Therefore, using the same spot-sizesof (e.g., 50 μm), and central distances from each line being 40, 45, 50,and 55 μm (for example; see FIG. 4 ), the contact angles increase asspacing is increased. Furthermore, in some embodiments, the measure ofadvancing and receding contact angles correspond to superhydrophobicbehaviour (i.e., above 150°) for line spacing of 55 μm and a hysteresisequal to 9.9°. FIG. 2A shows contact angle results and comparisons forhydrophobic surfaces according to some embodiments. Hydrophobic surfacesshow an increase as compared to a control in Advancing (Adv), Receding(Rec) and Static (Sta) contact angles. The graph also displays thedifference in contact angle according to the spacing and power used (seeFIG. 2B).

Surface morphology of the machined areas (according to some embodiments)can be examined using a scanning electron microscope (SEM). Hydrophobicsurfaces demonstrate an increase in roughness (see FIG. 3 ), due tonon-linear absorption by the PC of near-infrared high intensityfemtosecond laser. In some embodiments, the non-thermal characteristicsof the femtosecond laser do not allow for a reflow of polymer, andtherefore, the smoothing of the surface.

In addition to the rough surface, formation of crests of the same heightof non-ablated areas can be obtained, and, in some embodiments, due to alarger line spacing. Hence, along with the rough surface, crestsinfluence the difference in the contact angles. As shown in FIG. 2A, thelargest increase in hydrophobicity occurs in the largest spacing used(55 μm), whereas the lowest occurs at 40 μm spacing. Parallel crestswere seen in all but the 40 μm spacing as seen in FIG. 4 . Furthermore,lower spacing ablation generated an irregular surface that variedapproximately 4.0 μm in height. The highest ablation spacing (55 μm)using 13 mW power generated 20±2.5 μm grooves whilst 5 mW power 15±2.3μm. The change in power generated virtually no change in hydrophobicityfor the advancing and receding contact angles.

The optical profiler demonstrated that most of the increase inhydrophobicity due to the femtosecond laser ablation was generated bythe increase in surface roughness as seen in the 40 μm spacing sample inFIG. 4 , which illustrates optical profile measurements via a top viewand a cross-section view for hydrophobic surfaces at different linespacing for 13 mW laser power. Furthermore, the formation of squarecrests at larger spacing can be a factor in the increase in hydrophobicsurfaces.

Hydrophilic surface morphology and wettability, according to someembodiments, is via surface modification by a nanosecond laser. In someembodiments, a nanosecond laser is used at a plurality of overlappedspacings (e.g., three (3)), which can generate similar or the samecrests as that for hydrophobic surface modification. However, smoothnessof ablated areas result using a nanosecond laser which occurs through athermal degradation process. Therefore, heating caused by the nanosecondlaser is sufficient to melt the polymer, which is followed by a re-flowof the melted material, leading to the smooth surface (see. FIG. 5 ).

Other evidence of the heating and melting process is a deformation ofborders of the ablated area due to heat transfer, which does not occurin the faster pulses when using femtosecond laser, and the heatinginfluences the formation of smooth wave like structures, as opposed tothat with the hydrophobic surfaces, where the crests were sharp and hadsquare-like tops. In some embodiments, lower spacing ablation (8 μm)resulted in smaller wave patterns, due to melting, than that with largerspacing lines as illustrated in FIG. 6 . FIG. 6 illustrates the opticalprofile measurements with respect to a top view and a cross-section viewfor super-hydrophilic surfaces at different line spacing. The waves (ormicrochannels formed by ablation within the whole ablated area) and themelted area (white box) are also shown. As shown, the wave top formedduring ablation for 8, 10 and 12 μm spacings are 10.0±0.7, 5.5±0.8 and6.0±1.0 μm, respectively, below the ablation surface, and the bottoms ofthe waves are at 15.0±1.0, 12.0±0.8 13.0±1.0 μm, respectively.

Accordingly, in some embodiments, the grooves in the waves can lead tothe formation of smooth open capillaries, which can be approximately 10μm in width and 5.0, 6.5 and 7 μm in depth. The formation of these openmicro-channels within the ablated area is, in some embodiments, a factorfor creating a capillary force that pulls a liquid and results in azero-contact angle of the sample. Therefore, such a surface correspondsto a super-hydrophilic surface. Using a goniometer to record a sequenceof images at 100 ms interval, some of the results of which are shown inFIG. 7 , which shows the hydrophilicity of the surface, as compared to acontrol and hydrophobic static contact angles. The top left of FIG. 7shows a PC unmodified surface (78.5 deg.), the top-right showing afemtosecond laser modified surface (145 deg.), and the bottom showing ananosecond laser modified surface and its hydrophilic wetting behaviour.

Wettability of the ablated surface can verify the influence of thesurface pattern relative to chemical modification through a possibleinsertion of chemical groups (hydrophobic or super-hydrophilic) that mayaffect the interaction in the solid-liquid interface. Accordingly,samples area coated with gold in order to hinder the hydrophilic effectsdue to the change in surface chemistry, turning the hydrophilic surfaceinto hydrophobic. FIG. 8 shows, left to right, an increase ofhydrophobicity of the gold coated (blocked) hydrophilic surfaces createdin PC according to 8, 10 and 12 μm line spacings. The static contactangle for 8, 10 and 12 μm spacing samples were respectively 99.0±2.7,127.7.0±3.1, 144±4.0°. Therefore, this increase in contact angleconfirms that the hydrophilicity is due to the chemical change of thematerial. Furthermore, an airgap caused by the waves, induced aCassie-state of wettability, where the air pockets, located within thewaves crests, induce an increase in contact angle seen after thehydrophilic groups were covered by gold.

For example, in some embodiments, hydrophobic and super-hydrophilicsurfaces can include both morphological and chemical components. Forexample, an ATR-FTIR spectra of a PC sample before laser treatment andafter nanosecond and femtosecond laser treatment was evaluated and theresults of and it is shown in FIG. 9 . The spectra were normalized tothe same height for the 2966 cm⁻¹ (CH stretch mode for the methyl group)band to more easily visualize differences in the C—O and C═O groups,which are considered hydrophilic, caused by the different lasertreatment effects. The main peaks in the spectra were the C—H stretchmodes of methyl groups between 2800 to 3000 cm⁻¹, the sharp carbonylstretch around 1770 cm⁻¹, the phenol ring stretch at 1501 cm⁻¹, thecarbon-oxygen stretch (C(O)C) mode appearing as a broad band at 1220cm⁻¹ and 1011 cm⁻¹. Smaller bands due to the C—H stretch modes of thephenol rings appear between 3100-3000 cm⁻¹, whilst the bands at 830 cm⁻¹and 1880 cm⁻¹ were overtones and out-of-plane deformations ofpara-disubstituted phenol rings in the backbone of the PC.

The spectra differences in relative intensities, bandwidths and shiftswere apparent in some of the bands. The changes indicated surfacemodification due to thermal degradation, particularly for thenanosecond-lasered surface. The use of the nanosecond treatmentincreased the relative intensities of the C═O and O(C)O stretch modes atrespectively 1770 cm⁻¹ and 1218-1011 cm⁻¹, as well as red shifted bandsand broader bands for the nanosecond laser treated samples. The samechanges can also be observed for the deformation and twisting bonds forthe chains (CH₂). This could be explained by greater thermal degradationof the PC structures resulting in scission of the polymer chainsfollowed by branching, eventually leading to crosslinking and gelationor reflow of the surface material.

For the femtosecond treatment a slight broadening and increase infrequency and intensity can be observed in the CO stretch modes at 1221cm⁻¹. Furthermore, a small broadening in these bands is indicative of astructural change due to a small thermal effect, but in considerablylower effects than the nanosecond treatment. In addition, a smallincrease in the C═C stretch mode for the aromatic ring. The changes tothe femtosecond ablated surface are far fewer changes as the thermaldamage by this technique is small.

Accordingly, the ability to have high fluid control in microchannelscorresponds to the ability to miniaturize microfluidic circuits evenfurther. For example, in centrifugal microfluidics, the fluid can becontrolled using the forces derived from the disk spin, the capillaryforce due to the dimensions of the channels and wall wettability, asshown in FIG. 10 , the left-view of a channel showing θh, the right-topview is a control, right-center showing hydrophobic, and right-bottomview showing hydrophilic surfaces and corresponding wettability insideof a microchannel. The behaviour of the fluid being compressed inside amicro channel demonstrates that the modified hydrophobic surfacedisplays a Wenzel state; in other words, the droplets are in fullcontact with the rough surface. This is supported by the fluid behaviourin hydrophobic valves, which hold a water droplet even at the exittransition between the modified and unmodified surface. Therefore, theWenzel state is supported by chemical and morphological analysis, aswell as by the fluid behaviour inside of the microchannel. Investigationof a cross-view of the channels with the different surfaces show thathydrophobic and hydrophilic surfaces (top and bottom of channels)display similar wettability in a closed channel despite a completedifference in wettability on the open surface measurements.

An increase in wettability from both processed surfaces compared tocontrol have different effects on the liquid droplet and allowed fordifferent fluid manipulations. The hydrophobic valves show an increasein the necessary burst frequency from 648.5±49.6 to 817.6±35.4 rpm,leading to an experimental pressure increase, using:

$P_{burst} = {{\rho\Delta}R{\overset{\_}{R}( \frac{\pi.\omega}{30} )}^{2}}$

The increase is from 349.07±55.11 to 490.49±42.10 Pa. Hence, an increaseof approximately 29% in the pressure necessary to burst the hydrophobicvalves compared to the control. The theoretical pressure is calculatedusing:

${f_{0}({rpm})} = {( {\omega.\frac{30}{\pi}} ) = {\frac{30}{\pi}\sqrt{\frac{2\sigma{❘{{w\cos\theta_{h}} + {h\cos\theta_{w}}}❘}}{{hw}{\rho\Delta}{R.\overset{\_}{R}}}}}}$

which uses the contact angles and channel dimensions to find the angularvelocity then apply to the prior equation. The results, respectively:351.74±24.76 and 487.83±19.66 Pa, for the control and hydrophobic valve(thus, agreeing with the experimental values). In some embodiments,fluid stoppage directly on the initial part of the patch and the pictureof the inner channel, represents the stationary fluid.

Fluid movement behaviour in a super-hydrophilic surface according tosome embodiments have different phases related to how the fluid movesthrough a laser modified area. A first part, comprising a “speed lane”,which happens upon a droplet touching the modified surface. The highsurface energy on a super-hydrophilic portion quickly pulls the dropletto the end of the super-hydrophilic portion until it touches anunmodified area. Thus, the pressure necessary to move the dropletdecreases due to the high surface energy created by the associatedchemical modification. As soon as the droplet touches the lower surfaceenergy, unmodified area, the droplet requires more pressure to overcomethe unmodified area. Therefore, behaving similarly to a hydrophobicvalve. FIG. 11 illustrates these stages, specifically: (A) fluid ispushed towards the valve through the centrifugal force; (B) as soon asthe fluid touches the valve it is quickly pulled to the end of thevalve; and (C) once the meniscus passes through the valve, thehydrophilic valve works as valve (portion) holding the fluid and highercentrifugal force is needed to overcome the valve. It is worth notingthat (C) is also seen for the hydrophobic surfaces indicating Wenzelstate for the surface wettability.

The calculated pressure for the hydrophilic valve channels using thecontract angles and channel dimensions was 222.86±19.70 Pa. The fluidentered the hydrophilic patch at 662.50±48.20 rpm which wasapproximately the same speed necessary to burst the control channel.However, as soon as the droplet meniscus overcame the valve, the fluidwas held by the super-hydrophilic surface. The necessary speed torelease the droplet from the valve was 802.50±39.14 rpm. Resulting in adifference of 140.0±29.43 rpm for the necessary burst frequency forovercome the surface modified area. Applying this difference andcalculating the experimental burst pressure resulted in 212.55±34.87 Pa.A decrease of approximately 39% in the pressure required to move thedroplet through the channel. The calculated burst pressure using thecontact angle and dimension measurements, which resulted in 222.86±19.70Pa. The results are summarized in the table shown in FIG. 12 in which atheoretical pressure P calculated using the channel parameters (e.g.,contact angles and dimensions); the calculated pressure uses theacquired burst frequency.

Results indicate three (3) different possible uses of hydrophobicvalves: (1) use to stop fluids during first sample insertion, whichenables a more precise sample measurement; (2) the microfluidiccircuits, including channels, can be reduced in size, with the capillaryforce increasing, and therefore, the valves can stop fluid leaking on anext set of chambers before a desired time. Accordingly, the solventfree modifications presented according to some embodiments of thepresent disclosure allow for a more secure timing for the addition ofdifferent samples or reagents coming from other chambers as the pressurenecessary to burst the hydrophobic valve is considerably higher. Thecentrifugal force necessary to overcome a hydrophobic barrier with thesame dimensions of one without these hydrophobic regions is higher.Therefore, allowing for a more precise timing.

Thus, the production of super-hydrophilic areas/portions (e.g., valves)in embodiments of the present disclosure demonstrate a similar valveresult as the hydrophobic valves but via a different mechanism.Similarly, hydrophobic valves according to embodiments of the presentdisclosure also increased the burst pressure necessary to allow fluidmovement by holding the fluid in the modified area.

As centrifugal microfluidic miniaturize even further, super-hydrophilicportions can be used to hold microdroplets in position, whilst applyinga higher acceleration and deceleration (Euler force) and take advantageof mixing at micro or nano scales.

Moreover, hydrophilic valves according to some embodiments can be usedas a platform to increase the speed of transfer of liquids from onechamber to another in one or more fluid circuits. Thus, and for example,in the case of having a channel and chamber covered with asuper-hydrophilic surface according to some embodiments of the presentdisclosure, and a another without it, the modified channel and chambercan receive the liquid before a pressure threshold that is enough tohave the fluid moving through unmodified surfaces is reached.Furthermore, the super-hydrophilic surfaces according to someembodiments of the disclosure can be used in open-air microfluidiccircuits that require fluids to use capillary force, and, at the sametime, requiring the fluid to be held by such capillaries.

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means, steps, and/or structures for performing thefunction and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the inventiveembodiments described herein. More generally, those skilled in the artwill readily appreciate that all parameters, dimensions, materials, andconfigurations described herein are meant only to be examples and thatactual parameters, dimensions, materials, and configurations will dependupon the specific application or applications for which the inventiveteachings is/are used. Those skilled in the art will also recognize, orbe able to ascertain using no more than routine experimentation, manyequivalents to the specific inventive embodiments described herein. Itis, therefore, to be understood that the foregoing disclosed embodimentsare presented by way of example only and that, within the scope ofclaims supported by the present disclosure (including equivalentsthereto), inventive embodiments may be practiced otherwise than asspecifically described and claimed.

Some of the inventive embodiments of the present disclosure are directedto each individual feature, system, article, material, kit, method, andstep, described herein. In addition, any combination of two or more suchfeatures, systems, articles, materials, kits, methods, and steps, ifsuch features, systems, articles, materials, kits, methods, and steps,are not mutually inconsistent, is included within the inventive scope ofthe present disclosure. Some embodiments disclosed herein may also becombined with one or more features, as well as complete systems, devicesor methods of other embodiments (as well as known systems, devices, ormethods) to yield yet other embodiments and inventions. Moreover, someembodiments, may be distinguishable from the prior art by specificallylacking one and/or another feature disclosed in the particular prior artreference(s); i.e., claims to some embodiments may be distinguishablefrom the prior art by including one or more negative limitations.

Also, as shown above, various inventive concepts may be embodied as oneor more methods. The acts performed as part of the method may be orderedin any suitable way. Accordingly, embodiments may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative embodiments.

Any and all references to publications or other documents, including butnot limited to, patents, patent applications, articles, webpages, books,etc., presented anywhere in the present application, are hereinincorporated by reference in their entirety. Moreover, all definitions,as defined and used herein, should be understood to control overdictionary definitions, definitions in documents incorporated byreference, and/or ordinary meanings of the defined terms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The terms “can” and “may” are used interchangeably in the presentdisclosure, and indicate that the referred to element, component,structure, function, functionality, objective, advantage, operation,step, process, apparatus, system, device, result, or clarification, hasthe ability to be used, included, or produced, or otherwise stand forthe proposition indicated in the statement for which the term is used(or referred to) for a particular embodiment(s).

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e., “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of.” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

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What is currently claimed:
 1. A method of making a hydrophobic and/or asuper-hydrophilic areas on at least one surface of a substrate,comprising: machining, using laser ablation, at least a portion of theat least one surface of the substrate or film via a plurality of spotpulses from a laser to form, via a mask or a spatial light modulator(SLM), at least one of a super-hydrophilic area and a hydrophobic area,wherein: for the super-hydrophilic area, the laser comprises ananosecond laser, and for the hydrophobic area and/or a hydrophobicarea, the laser comprises a femtosecond laser.
 2. The method of claim 1,wherein the power of the nanosecond laser is configured based on thedepth of ablation desired.
 3. The method of claim 1, wherein awavelength of the nanosecond laser is selected from the group consistingof: between 150-400 nm, 150-350 nm, 150-300 nm, 150-250 nm, 150-200 nm,200-400 nm, 250-400 nm, 300-400 nm, and 350-400 nm,
 4. The method ofclaim 1, wherein a wavelength of the nanosecond laser is selected in theUV range.
 5. The method of claim 1, wherein the nanosecond laser is a UVlaser.
 6. The method of claim 1, wherein the femtosecond laser is an IRlaser.
 7. The method of claim 1, wherein a wavelength of the nanosecondlaser is 248 nm.
 8. The method of claim 1, wherein the spot pulses ofthe nanosecond laser are delivered for a duration selected from thegroup consisting of: between 0.1-50 ns, between 0.1-40 ns, between0.1-30 ns, between 0.1-20 ns, between 0.1-10 ns, between 0.1-5 ns,between 0.1-1 ns, between 0.5-50 ns, between 1-50 as, between 5-50 ns,between 10-50 ns, between 15-50 ns, between 20-50 ns, between 25-50 ns,between 30-50 ns, between 35-50 ns, between 40-50 ns, and between 45-50ns.
 9. The method of claim 1, wherein a repetition rate of thenanosecond laser is selected from the group consisting of: between: 1Hz-5 kHz, 1 Hz-4 kHz, 1 Hz-3 kHz, 1 Hz-2 kHz, 250 Hz-5 kHz, 250 Hz-4kHz, 250 Hz-3 kHz, 500 Hz-5 kHz, 500 Hz-4 kHz, 500 Hz-5 kHz, 1-5 kHz,1-4 kHz, 1-3 kHz, 1-2 kHz, 2-5 kHz, 2-4 kHz, 2-3 kHz, 3-5 kHz, 3-4 kHz,and 4-5 kHz.
 10. The method of claim 1, wherein a repetition rate of thenanosecond laser comprises 500 Hz.
 11. The method of claim 1, wherein aspot pulse size established by the nanosecond laser is selected from thegroup consisting of: between 10-10,000 μm², between 100-10,000 μm²,between 250-10,000 μm², between 500-10,000 μm², between 750-10,000 μm²,between 1,000-10,000 μm², between 2,000-10,000 μm², between 3,000-10,000μm², between 4,000-10,000 μm², between 5,000-10,000 μm², between6,000-10,000 μm², between 7,000-10,000 μm², between 8,000-10,000 μm²,between 9,000-10,000 μm², between 10-1,000 μm², between 10-2,000 μm²,between 10-3,000 μm², between 10-4,000 μm², between 10-5,000 μm²,between 10-6,000 μm², between 10-7,000 μm², between 10-8,000 μm²,between 10-9,000 μm², between 1,000-2,000 μm², between 1,000-3,000 μm²,between 1,000-4,000 μm², between 1,000-5,000 μm², between 1,000-6,000μm², between 1,000-7,000 μm², between 1,000-8,000 μm², between1,000-9,000 μm², between and 1,000-10,000 μm².
 12. The method of claim1, wherein a spacing between spot pulses of the nanosecond laser isselected from the group consisting of: between 1-100,000 nm, between1-75,000 nm, between 1-50,000 nm, between 1-25,000 nm, between 1-20,000nm, between 1-15,000 nm, between 1-10,000 nm, between 1-5,000 nm,between 1-4,000 nm, between 1-3,000 nm, between 1-2,000 nm, between1-1,000 nm, between 1000-100,000 nm, between 10,000-100,000 nm, between25,000-100,000 nm, between 50,000-100,000 nm, and between 75,000-100,000nm.
 13. The method of claim 1, wherein a spacing between lines of spotpulses of the nanosecond laser is selected from the group consisting of:between 1 nm-1000 μm, between 1 nm-750 μm, between 1 nm-500 μm, between1 nm-250 μm, between 1 nm-100 μm, between 1 nm-50 μm, between 1 nm-10μm, between 1 nm-1 μm, between 10 nm-1000 μm, between 100 nm-1000 μm,between 1 nm-1000 μm, between 10 μm-1000 μm, between 100 μm-1000 μm,between 250 μm-1000 μm, between 500 μm-1000 μm, between 750 μm-1000 μm,between 800 μm-1000 μm, and between 900 μm-1000 μm.
 14. The method ofclaim 1, wherein the nanosecond laser establishes the super-hydrophilicarea within a channel, having a contact angle of less than 50 deg. 15.The method of claim 1, wherein the power of the femtosecond laser isconfigured based on the depth of ablation desired.
 16. The method ofclaim 1, wherein the power of the femtosecond laser is selected from thegroup consisting of: between 1-1000 mW, between 10-1000 mW, between25-1000 mW, between 50-1000 mW, between 100-1000 mW, between 250-1000mW, between 300-1000 mW, between 400-1000 mW, between 500-1000 mW,between 750-1000 mW, between 800-1000 mW, between 900-1000 mW, between1-900 mW, between 1-800 mW, between 1-700 mW, between 1-600 mW, between1-500 mW, between 1-400 mW, between 1-300 mW, between 1-200 mW, between1-100 mW, between 1-50 mW, between 1-25 mW, between 1-20 mW, between1-15 mW, between 1-10 mW, and between 1-5 mW.
 17. The method of claim 1,wherein a wavelength of the femtosecond laser is selected from the groupconsisting of: between 680-1130 nm, between 680-1000 nm, between 680-900am, between 680-800 nm, between 680-700 nm, between 700-1130 nm, between800-1130 nm, between 900-1130 nm, and between 1000-1130 nm.
 18. Themethod of claim 1, wherein the spot pulses of the femtosecond laserbetween 25-400 fs, between 50-400 fs, between 75-400 fs, between 100-400fs, between 150-400 fs, between 200-400 fs, between 250-400 fs, between300-400 fs, between 350-400 fs, between 10-300 fs, between 10-200 fs,between 10-100 fs, between 10-75 fs, between 10-50 fs, and between 10-25fs.
 19. The method of claim 10, wherein a repetition rate of thefemtosecond laser is selected from the group consisting of: between 500Hz-300 kHz, between 500 Hz-200 kHz, between 500 Hz-100 kHz, between 500Hz-50 kHz, between 500 Hz-10 kHz, between 500 Hz-5 kHz, between 500 Hz-1kHz, between 500 Hz-750 Hz, between 750 Hz-300 kHz, between kHz-300 kHz,between 1.5 kHz-300 kHz, between 2 kHz-300 kHz, between 5 kHz-300 kHz,between 10 kHz-300 kHz, between 25 kHz-300 kHz, between 50 kHz-300 kHz,between 100 kHz-300 kHz, between 150 kHz-300 kHz, between 200 kHz-300kHz, and between 250 kHz-300 kHz.
 20. The method of claim 10, wherein arepetition rate of the femtosecond laser comprises 1 kHz.
 21. The methodof claim 10, wherein a spot size established by the femtosecond laser isselected from the group consisting of: between 1-2500 μm², between1-2000 μm², between 1-1500 μm², between 1-1000 μm², between 1-750 μm′,between 1-500 μm², between 1-250 μm², between 1-100 μm², between 1-75μm², between 1-50 μm², between 1-25 μm², between 1-10 μm², between 1-5μm², between 1-2 μm², between 10-2500 μm², between 25-2500 μm², between50-2500 μm², between 75-2500 μm², between 100-2500 μm², between 250-2500μm², between 500-2500 μm, between 750-2500 μm², between 1000-2500 μm²,between 1250-2500 μm², between 1500-2500 μm², between 1750-2500 μm²,between 2000-2500 μm², and between 2250-2500 μm²,
 22. The method ofclaim 10, wherein a spacing between spot pulses of the femtosecond laseris selected from the group consisting of: between 500 nm-100 μm, between1 μm-100 μm, between 10 μm-100 μm, between 25 μm-100 μm, between 50μm-100 μm, between 75 μm-100 μm, between 80 μm-100 μm, between 90 μm-100μm, between 500 nm-90 μm, between 500 nm-75 μm, between 500 nm-50 μm,between 500 nm-25 μm, between 500 nm-10 μm, between 500 nm-5 μm, between500 nm-2 μm, and between 500 nm-1 μm.
 23. The method of claim 1, whereina spacing between lines of spot pulses of the femtosecond laser isselected from the group consisting of: between 100 nm-1.00 μm, between2500 nm-100 μm, between 500 nm-100 μm, between 750 nm-100 μm, between 1μm-100 μm, between 2 μm-100 μm, between 5 μm-100 μm, between 10 μm-100μm, between 25 μm-100 μm, between 30 μm-100 μm, between 40 μm-100 μm,between 50 μm-100 μm, between 75 μm-100 μm, between 80 μm-100 μm,between 90 μm-100 μm, between 100 nm-100 μm, between 100 nm-75 μm,between 1.00 nm-50 μm, between 100 nm-25 μm, between 100 nm-20 μm,between 100 nm-10 μm, between 100 nm-5 μm between 100 nm-2 μm, between1.00 nm-1 μm, between 100 nm-900 nm, between 100 nm-750 nm, between 100nm-500 nm, between 100 nm-250 nm, between 100 nm-200 nm, and between 100nm-150 nm.
 24. The method of claim 1, wherein the femtosecond laserestablishes the hydrophobic area within a channel, such that, a contactangle θ of 90 degrees or greater.
 25. The methods of any of claim 1,wherein the substrate comprises a polycarbonate (PC) substrate or film,or a substrate or film material including properties similar to PC. 26.The methods of claim 1, wherein the substrate or film is adhered to oneor more additional layers.
 27. The method of claim 26, wherein die oneor more additional layers comprise one or more of: at least one layer ofpolyethylene terephthalate (PET), at least one layer of polycarbonate(PC), at least one surface, at least one layer of polymethylmethacrylate (PMMA), and at least one layer of a pressure sensitiveadhesive (PSA) arranged between adjacent layers.
 28. The method of claim1, wherein at least one of the super-hydrophilic areas and/or thehydrophobic areas are configured as valves for a microfluidic circuit,device, or channel.